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(#) Missing Constraints in ConstraintLayout

!!! ERROR: Missing Constraints in ConstraintLayout
   This is an error.

Id
:   `MissingConstraints`
Summary
:   Missing Constraints in ConstraintLayout
Severity
:   Error
Category
:   Correctness
Platform
:   Android
Vendor
:   Android Open Source Project
Feedback
:   https://issuetracker.google.com/issues/new?component=192708
Since
:   2.2.0 (September 2016)
Affects
:   Resource files
Editing
:   This check runs on the fly in the IDE editor
Implementation
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-checks/src/main/java/com/android/tools/lint/checks/ConstraintLayoutDetector.kt)
Tests
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/ConstraintLayoutDetectorTest.kt)

The layout editor allows you to place widgets anywhere on the canvas,
and it records the current position with designtime attributes (such as
`layout_editor_absoluteX`). These attributes are **not** applied at
runtime, so if you push your layout on a device, the widgets may appear
in a different location than shown in the editor. To fix this, make sure
a widget has both horizontal and vertical constraints by dragging from
the edge connections.

(##) Example

Here is an example of lint warnings produced by this check:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text
res/layout/layout1.xml:11:Error: This view is not constrained. It only
has designtime positions, so it will jump to (0,0) at runtime unless you
add the constraints [MissingConstraints]
    &lt;TextView
     --------
res/layout/layout1.xml:16:Error: This view is not constrained. It only
has designtime positions, so it will jump to (0,0) at runtime unless you
add the constraints [MissingConstraints]
    &lt;TextView
     --------
res/layout/layout1.xml:38:Error: This view is not constrained
vertically: at runtime it will jump to the top unless you add a vertical
constraint [MissingConstraints]
    &lt;TextView
     --------
res/layout/layout1.xml:47:Error: This view is not constrained
horizontally: at runtime it will jump to the left unless you add a
horizontal constraint [MissingConstraints]
    &lt;TextView
     --------
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here is the source file referenced above:

`res/layout/layout1.xml`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~xml linenumbers
&lt;androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:layout_editor_absoluteX="0dp"
    tools:layout_editor_absoluteY="81dp"
    tools:context="test.pkg.myapplication.MainActivity"
    tools:ignore="HardcodedText"&gt;
    &lt;TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Not constrained and no designtime positions" /&gt;
    &lt;TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Not constrained"
        tools:layout_editor_absoluteX="21dp"
        tools:layout_editor_absoluteY="23dp" /&gt;
    &lt;TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Constrained both"
        app:layout_constraintBottom_creator="2"
        app:layout_constraintBottom_toBottomOf="@+id/activity_main"
        app:layout_constraintLeft_creator="2"
        app:layout_constraintLeft_toLeftOf="@+id/activity_main"
        app:layout_constraintRight_creator="2"
        app:layout_constraintRight_toRightOf="@+id/activity_main"
        app:layout_constraintTop_creator="2"
        app:layout_constraintTop_toTopOf="@+id/activity_main"
        tools:layout_editor_absoluteX="139dp"
        tools:layout_editor_absoluteY="247dp" /&gt;
    &lt;TextView
        android:id="@+id/textView4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Constrained Horizontally"
        app:layout_constraintLeft_creator="0"
        app:layout_constraintLeft_toLeftOf="@+id/textView3"
        tools:layout_editor_absoluteX="139dp"
        tools:layout_editor_absoluteY="270dp" /&gt;
    &lt;TextView
        android:id="@+id/textView5"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Constrained Vertically"
        app:layout_constraintBaseline_creator="2"
        app:layout_constraintBaseline_toBaselineOf="@+id/textView4"
        tools:layout_editor_absoluteX="306dp"
        tools:layout_editor_absoluteY="270dp" /&gt;
    &lt;androidx.constraintlayout.widget.Guideline
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/androidx.constraintlayout.widget.Guideline"
        app:orientation="vertical"
        tools:layout_editor_absoluteX="20dp"
        tools:layout_editor_absoluteY="0dp"
        app:relativeBegin="20dp" /&gt;
    &lt;requestFocus/&gt;
&lt;/androidx.constraintlayout.widget.ConstraintLayout&gt;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can also visit the
[source code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/ConstraintLayoutDetectorTest.kt)
for the unit tests for this check to see additional scenarios.

The above example was automatically extracted from the first unit test
found for this lint check, `ConstraintLayoutDetector.testMissingConstraints`.
To report a problem with this extracted sample, visit
https://issuetracker.google.com/issues/new?component=192708.

(##) Suppressing

You can suppress false positives using one of the following mechanisms:

* Adding the suppression attribute `tools:ignore="MissingConstraints"`
  on the problematic XML element (or one of its enclosing elements).
  You may also need to add the following namespace declaration on the
  root element in the XML file if it's not already there:
  `xmlns:tools="http://schemas.android.com/tools"`.

  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;android.support.constraint.ConstraintLayout xmlns:tools="http://schemas.android.com/tools"
      tools:ignore="MissingConstraints" ...&gt;
    ...
  &lt;/android.support.constraint.ConstraintLayout&gt;
  ```

* Using a special `lint.xml` file in the source tree which turns off
  the check in that folder and any sub folder. A simple file might look
  like this:
  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;lint&gt;
      &lt;issue id="MissingConstraints" severity="ignore" /&gt;
  &lt;/lint&gt;
  ```
  Instead of `ignore` you can also change the severity here, for
  example from `error` to `warning`. You can find additional
  documentation on how to filter issues by path, regular expression and
  so on
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html).

* In Gradle projects, using the DSL syntax to configure lint. For
  example, you can use something like
  ```gradle
  lintOptions {
      disable 'MissingConstraints'
  }
  ```
  In Android projects this should be nested inside an `android { }`
  block.

* For manual invocations of `lint`, using the `--ignore` flag:
  ```
  $ lint --ignore MissingConstraints ...`
  ```

* Last, but not least, using baselines, as discussed
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).

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